The present application relates to vehicles moving backwards, and is particularly directed to a backward movement indicator apparatus for a vehicle, such as a truck.
When a truck driver desires to backup the truck, the driver shifts transmission of the truck into reverse gear. In some trucks, a position sensor is operatively coupled to the transmission to detect when the transmission is in reverse gear. The reverse gear position sensor provides a signal when the reverse gear position sensor detects that the transmission is in reverse gear. A drawback in using a reverse gear position sensor is that sometimes the truck may not actually be moving backwards even though the signal from the reverse gear position sensor indicates otherwise. Another drawback in using a reverse gear position sensor is that sometimes the truck can be moving backwards without the transmission being in reverse gear. A reverse gear position sensor can therefore sometimes provide either a false indication of the truck moving backwards or a false indication of the truck not moving backwards.
In some other trucks, a speed sensor is operatively coupled to a wheel of the truck to provide a signal indicative of ground speed of the vehicle. In this case, some types of wheel speed sensors and exciter ring assemblies provide a signal indicative of the truck moving backwards when the wheel speed sensor detects that the truck wheels are turning in the backward direction at a rate which exceeds a predetermined rate. A drawback in using a wheel speed sensor is that sometimes the truck may actually be moving backwards even though the signal from the wheel speed sensor indicates otherwise. This can occur because a typical variable reluctance wheel speed sensor does not produce an output at very tow wheel turning speeds such as when the truck is rolling slowly backwards. It would be desirable to provide a reverse movement indicator apparatus which provides a true indication of when the truck is actually moving backwards.